Fastener members, having a flange portion and a hollow barrel portion with a flarable end, are known and are commonly referred as Tee-nuts, or rivet type Tee-nuts. In this specification, the term "Tee-nut" is used to describe such fastener members.
Such Tee-nuts are usually formed of sheet metal, and provide a flange portion with a plurality of fastening teeth or prongs, and a threaded sleeve or barrel, all formed out of a single piece of sheet metal.
Typically such Tee-nuts are used, for example, in furniture frames, for fastening the arms and legs of the furniture to the frame. They also have a variety of other uses, both in furniture and in many other industries.
U.S. Pat. No. 5,348,432 granted to Nagayama on Sep. 20, 1994 discloses a Tee-nut having a sleeve in the form of a hollow cylinder with a relatively thin-walled flarable end portion and a relatively thicker-walled threaded portion. The thin-walled flarable hollow sleeve end is formed by counter boring an internally threaded hollow sleeve. The disadvantage of this product is that counter boring is uneconomical to perform. Also, tiny metal scraps are likely to be left behind within the internal threads. Also, when flared outwardly, the thin-walled flarable counter-bored end has a tendency to split, and the thin walled portion has a tendency to collect wood chips internally in the threads.
U.S. Pat. No. 5,618,144, inventor Volkmar W. Leistner, title Tee-nut with Enlarged Barrel End, granted Apr. 8, 1997 and assigned to Sigma Tool & Machine a Partnership of Sigma Tool & Machine Limited and Sigma Fasteners Limited shows an improved form of Tee-nut with a flarable end. In this patent the Tee-nut barrel is swaged out to enlarge its diameter, without counterboring and weakening the flarable portion. However, these Tee-nuts require to be inserted into and through a bore in a wooden workpiece. The enlarged flarable leading end which was inserted first into the bore tended to cause unnecessary problems, since the leading end of the open bore tended to catch on the wood or tear particles of wood away.